1. Copy them

This strategy is called mirroring, and involves subtly mimicking the other person's behavior. When talking to someone, try copying their body language, gestures, and facial expressions.

In 1999, New York University researchers documented the "chameleon effect," which occurs when people unconsciously mimic each other's behavior, and that mimicry facilitates liking.

Researchers had 78 men and women work on a task with a partner, who was really a confederate working for the researchers. The partners engaged in different levels of mimicry, while researchers secretly videotaped the interactions. At the end of the interaction, the researchers had participants indicate how much they liked those partners.

Sure enough, participants were more likely to say that they liked their partner when their partner had mimicked their behavior.

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2. Spend more time around them

According to the mere-exposure effect, people tend to like things that are familiar to them.

Knowledge of this phenomenon dates back to the 1950s, when MIT researchers discovered that college students who lived closer together in housing projects were more likely to be friends than students who lived farther apart.

This could be because students who live close by can experience more passive, day-to-day interactions with each other, such as greeting each other in the common room or kitchen. Under certain circumstances, those interactions can develop into full-fledged friendships.

More recently, psychologists at the University of Pittsburgh had four women pose as students in a university psychology class. Each woman showed up in class a different number of times. When experimenters showed male students pictures of the four women, the men demonstrated a greater affinity for those women they'd seen more often in class — even though they hadn't interacted with any of them.

Taken together, these findings suggest that simply spending more time with people can make them like you more. Even if you don't live near your friends, try sticking to a steady routine with them, such as going out for coffee every week or taking a class together.

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3. Compliment other people

People will associate the adjectives you use to describe other people with your personality. This phenomenon is called spontaneous trait transference.

One study found that this effect occurred even when people knew certain traits didn't describe the people who had talked about them.

If you describe someone else as genuine and kind, people will also associate you with those qualities. The reverse is also true: If you are constantly trashing people behind their backs, your friends will start to associate the negative qualities with you as well.

4. Be in a great mood

Emotional contagion describes what happens when people are strongly influenced by the moods of other people. According to a research paper from the Ohio University and the University of Hawaii, people can unconsciously feel the emotions of those around them.

If you want to make others feel happy when they're around you, do your best to communicate positive emotions.

5. Make friends with their friends

The social-network theory behind this effect is called triadic closure, which means that two people are likely to be closer when they have a common friend.

To illustrate this effect, students at the University of British Columbia designed a program that friends random individuals on Facebook. They found that people were more likely to accept their friend request as their number of mutual friends increased — from 20% with no mutual friends to close to 80% with more than 11 mutual friends.

6. Don't be complimentary all the time

The gain-loss theory of interpersonal attractiveness suggests that your positive comments will make more of an impact if you deliver them only occasionally.

A 1965 study by University of Minnesota researchers shows how this theory might work in practice. Researchers had 80 female college students work in pairs on a task and then allowed those students to "overhear" their partners talking about them. In reality, experimenters had told the partners what to say.

In one scenario, the comments were all positive; in a second scenario, the comments were all negative; in a third scenario, the comments went from positive to negative; and in a fourth scenario, the comments went from negative to positive.

As it turns out, students liked their partners best when the comments went from positive to negative, suggesting that people like to feel that they've won you over in some capacity.

7. Be warm and competent

According to the model, if you can portray yourself as warm — i.e., noncompetitive and friendly — people will feel like they can trust you. If you seem competent — for example, if you have high economic or educational status — they're more inclined to respect you.

Harvard psychologist Amy Cuddy says that, especially in business settings, it's important to demonstrate warmth first and then competence.

"From an evolutionary perspective," Cuddy writes in her book "Presence," "it is more crucial to our survival to know whether a person deserves our trust."

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8. Reveal your flaws from time to time

According to the pratfall effect, people will like you more after you make a mistake — but if they only believe you are usually a competent person. Revealing that you aren't perfect makes you more relatable and vulnerable toward the people around you.

Researcher Elliot Aronson first discovered this phenomenon when he studied how simple mistakes can affect perceived attraction. He asked male students from the University of Minnesota to listen to tape recordings of people taking a quiz.

When people did well on the quiz but spilled coffee at the end of the interview, the students rated them higher on likability than when they did well on the quiz and didn't spill coffee or didn't do well on the quiz and spilled coffee.

9. Emphasize your shared values

According to a classic study by Theodore Newcomb,people are more attracted to those who are similar to them. This is known as the similarity-attraction effect. In his experiment, Newcomb measured his subjects' attitudes on controversial topics, such as sex and politics, and then put them in a University of Michigan-owned house to live together.

By the end of their stay, the subjects liked their housemates more when they had similar attitudes about the topics that were measured.

If you're hoping to get friendly with someone, try to find a point of similarity between you two and highlight it.

10. Casually touch them

This is known as subliminal touching, which occurs when you touch a person so subtly that they barely notice. Common examples include tapping someone's back or touching their arm, which can make them feel more warmly toward you.

In "Subliminal: How Your Unconscious Mind Rules Your Behavior," author Leonard Mlodinow mentions a study in France in which young men stood on street corners and talked to women who walked by. They had double the success rate in striking up a conversation when they lightly touched the woman's arms as they talked to them instead of doing nothing at all.

In a University of Mississippi and Rhodes College experiment that studied the effects of interpersonal touch on restaurant tipping, waitresses briefly touched customers on the hand or shoulder as they were returning their change. As it turns out, they earned significantly larger tips than waitresses who didn't touch their customers.

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11. Smile

In one study, nearly 100 undergraduate women looked at photos of another woman in one of four poses: smiling in an open-body position, smiling in a closed-body position, not smiling in an open-body position, or not smiling in a closed-body position. Results suggested that the woman in the photo was liked most when she was smiling, regardless of her body position.

12. See the other person how they want to be seen

People want to be perceived in a way that aligns with their own beliefs about themselves. This phenomenon is described by self-verification theory. We all seek confirmations of our views, positive or negative.

For a series of studies at Stanford University and the University of Arizona, participants with positive and negative perceptions of themselves were asked whether they wanted to interact with people who had positive or negative impressions of them.

The participants with positive self-views preferred people who thought highly of them, while those with negative self-views preferred critics. This could be because people like to interact with those who provide feedback consistent with their known identity.

Other research suggests that, when people's beliefs about us line up with our own, our relationship with them flows more smoothly. That's likely because we feel understood, which is an important component of intimacy.

13. Tell them a secret

Self-disclosure may be one of the best relationship-building techniques.

In a study led by Arthur Aron at Stony Brook University, college students were paired off and told that they should spend 45 minutes getting to know each other better.

Experimenters provided some student pairs with a series of questions to ask, which got increasingly deep and personal. For example, one of the intermediate questions was "How do you feel about your relationship with your mother?" Other pairs were given small-talk-type questions. For example, one question was "What is your favorite holiday? Why?"

You can try this technique on your own as you're getting to know someone. For example, you can build up from asking them about their last trip to the movies to learning about the people who mean the most to them in life. When you learn intimate information about another person, they are likely to feel closer to you and want to confide in you in the future.

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14. Expect good things from people

According to the Pygmalion effect, people treat others in ways that are consistent with their expectations of them and therefore cause the person to behave in a way that confirms those expectations.

In a Harvard Magazine article, Cuddy says, "If you think someone's a jerk, you'll behave toward them in a way that elicits jerky behaviors."

On the other hand, if you expect someone to be friendly toward you, they are more likely to behave in a friendly manner toward you.

Meanwhile, not having a sense of humor, especially at the office, could backfire. One study of 140 Chinese workers between 26 and 35 found that people were less well-liked and less popular among their colleagues if they were "morally focused."

That means they placed a high value on displaying caring, fairness, and other moral traits. The researchers said that that was because morally focused individuals were perceived as less humorous by their colleagues.

17. Let them talk about themselves

Harvard researchers recently discovered that talking about yourself may be inherently rewarding, the same way that food, money, and sex are.

In one study, the researchers had participants sit in an fMRI machine and respond to questions about either their own opinions or someone else's. Participants had been asked to bring a friend or family member to the experiment, who was sitting outside the fMRI machine. In some cases, participants were told that their responses would be shared with the friend or relative; in other cases, their responses would be kept private.

Results showed that the brain regions associated with motivation and reward were most active when participants were sharing information publicly — but also when they were talking about themselves, even if no one was listening.

In other words, letting someone share a story or two about their life instead of blabbing on about yours could give them more positive memories of your interaction.